1. Field of the Invention
The present invention relates to a predistorter used in, for example, an amplifier apparatus having a predistortion system distortion compensating function for compensating for a distortion generated in an amplifier in amplifying an input signal by the amplifier by a predistortion system, particularly relates to a predistoter for compensating for a nonlinear distortion by a memory effect generated at an amplifier.
2. Description of Related Art
In, for example, a base station apparatus of a mobile communication system, at an amplifying portion of a transmitter, a signal constituting an object of transmission is amplified by an amplifier. Further, a nonlinear distortion is generated at the amplifier in accordance with a level of an input signal or the like and therefore, a distortion is compensated for by a predistortion system or the like.    Patent Reference 1: JP-T-2001-507196    Patent Reference 2: JP-T-8-504550    Patent Reference 3: Japanese Patent Publication No. 3051984    Patent Reference 4: Japanese Patent Publication No. 32293335    Patent Reference 5: U.S. Pat. No. 5,164,678    Nonpatent Reference 1: Kawaguchi, Akaiwa “Nonlinearity Compensation with Adaptive Predistorter for an Amplifier Affected by Even-order Distortion”, Shingaku Giho, MW2002-208 (2003-03) p. 63–66
However, according to the predistortion system of the background art, there is a drawback that it is not sufficient yet to effectively compensate for both of a nonlinear distortion by AM (Amplitude)— AM (Amplitude) conversion and AM (Amplitude)— PM (Phase) conversion and a distortion by a memory effect.